Telemetry media Seek action and metrics.

tools/telemetry/telemetry/page/actions/media_action.js

Index: tools/telemetry/telemetry/page/actions/media_action.js
diff --git a/tools/telemetry/telemetry/page/actions/media_action.js b/tools/telemetry/telemetry/page/actions/media_action.js
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+++ b/tools/telemetry/telemetry/page/actions/media_action.js
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+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+// This file provides common functions for media actions.
+window.__findMediaElements = function(selector) {
+  // Returns elements matching the selector, otherwise returns the first video
+  // or audio tag element that can be found.
+  // If selector == 'all', returns all media elements.
+  if (selector == 'all') {
+    return document.querySelectorAll('video, audio');
+  } else if (selector) {
+    return document.querySelectorAll(selector);
+  } else {
+    var media = document.getElementsByTagName('video');
+    if (media.length > 0) {
+      return [media[0]];
+    } else {
+      media = document.getElementsByTagName('audio');
+      if (media.length > 0) {
+        return [media[0]];
+      }
+    }
+  }
+  console.error('Could not find any media elements matching: ' + selector);
+  return [];
+};
+
+window.__hasEventCompleted = function(selector, event_name) {
+  // Return true if the event_name fired for media satisfying the selector.
+  var mediaElements = window.__findMediaElements(selector);
+  for (var i = 0; i < mediaElements.length; i++) {
+    if (!mediaElements[i][event_name + '_completed'])
+      return false;
+  }
+  return true;
+};